| Message ID | 1c9ef22826f449a3756bb13a83494e9fe3e0be8b.1696676782.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] dmaengine: pxa_dma: Remove an erroneous BUG_ON() in pxad_free_desc() | expand |
On Sat, Oct 07, 2023 at 01:13:10PM +0200, Christophe JAILLET wrote: > Prepare for the coming implementation by GCC and Clang of the __counted_by > attribute. Flexible array members annotated with __counted_by can have > their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS > (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family > functions). > > To do so, the code needs a little shuffling related to how hw_desc is used > and nb_desc incremented. > > The one by one increment is needed for the error handling path, calling > pxad_free_desc(), to work correctly. > > So, add a new intermediate variable, desc, to store the result of the > dma_pool_alloc() call. > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> Thanks! Yeah, this looks like a sensible refactor to handle the increment before array assignment without losing error checking. Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > --- > This patch is part of a work done in parallel of what is currently worked > on by Kees Cook. > > My patches are only related to corner cases that do NOT match the > semantic of his Coccinelle script[1]. > > [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci > --- > drivers/dma/pxa_dma.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c > index 94cef2905940..c6e2862896e3 100644 > --- a/drivers/dma/pxa_dma.c > +++ b/drivers/dma/pxa_dma.c > @@ -91,7 +91,8 @@ struct pxad_desc_sw { > bool cyclic; > struct dma_pool *desc_pool; /* Channel's used allocator */ > > - struct pxad_desc_hw *hw_desc[]; /* DMA coherent descriptors */ > + struct pxad_desc_hw *hw_desc[] __counted_by(nb_desc); > + /* DMA coherent descriptors */ > }; > > struct pxad_phy { > @@ -739,6 +740,7 @@ pxad_alloc_desc(struct pxad_chan *chan, unsigned int nb_hw_desc) > { > struct pxad_desc_sw *sw_desc; > dma_addr_t dma; > + void *desc; > int i; > > sw_desc = kzalloc(struct_size(sw_desc, hw_desc, nb_hw_desc), > @@ -748,20 +750,21 @@ pxad_alloc_desc(struct pxad_chan *chan, unsigned int nb_hw_desc) > sw_desc->desc_pool = chan->desc_pool; > > for (i = 0; i < nb_hw_desc; i++) { > - sw_desc->hw_desc[i] = dma_pool_alloc(sw_desc->desc_pool, > - GFP_NOWAIT, &dma); > - if (!sw_desc->hw_desc[i]) { > + desc = dma_pool_alloc(sw_desc->desc_pool, GFP_NOWAIT, &dma); > + if (!desc) { > dev_err(&chan->vc.chan.dev->device, > "%s(): Couldn't allocate the %dth hw_desc from dma_pool %p\n", > __func__, i, sw_desc->desc_pool); > goto err; > } > > + sw_desc->nb_desc++; > + sw_desc->hw_desc[i] = desc; > + > if (i == 0) > sw_desc->first = dma; > else > sw_desc->hw_desc[i - 1]->ddadr = dma; > - sw_desc->nb_desc++; > } > > return sw_desc; > -- > 2.34.1 >
diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c index 94cef2905940..c6e2862896e3 100644 --- a/drivers/dma/pxa_dma.c +++ b/drivers/dma/pxa_dma.c @@ -91,7 +91,8 @@ struct pxad_desc_sw { bool cyclic; struct dma_pool *desc_pool; /* Channel's used allocator */ - struct pxad_desc_hw *hw_desc[]; /* DMA coherent descriptors */ + struct pxad_desc_hw *hw_desc[] __counted_by(nb_desc); + /* DMA coherent descriptors */ }; struct pxad_phy { @@ -739,6 +740,7 @@ pxad_alloc_desc(struct pxad_chan *chan, unsigned int nb_hw_desc) { struct pxad_desc_sw *sw_desc; dma_addr_t dma; + void *desc; int i; sw_desc = kzalloc(struct_size(sw_desc, hw_desc, nb_hw_desc), @@ -748,20 +750,21 @@ pxad_alloc_desc(struct pxad_chan *chan, unsigned int nb_hw_desc) sw_desc->desc_pool = chan->desc_pool; for (i = 0; i < nb_hw_desc; i++) { - sw_desc->hw_desc[i] = dma_pool_alloc(sw_desc->desc_pool, - GFP_NOWAIT, &dma); - if (!sw_desc->hw_desc[i]) { + desc = dma_pool_alloc(sw_desc->desc_pool, GFP_NOWAIT, &dma); + if (!desc) { dev_err(&chan->vc.chan.dev->device, "%s(): Couldn't allocate the %dth hw_desc from dma_pool %p\n", __func__, i, sw_desc->desc_pool); goto err; } + sw_desc->nb_desc++; + sw_desc->hw_desc[i] = desc; + if (i == 0) sw_desc->first = dma; else sw_desc->hw_desc[i - 1]->ddadr = dma; - sw_desc->nb_desc++; } return sw_desc;
Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions). To do so, the code needs a little shuffling related to how hw_desc is used and nb_desc incremented. The one by one increment is needed for the error handling path, calling pxad_free_desc(), to work correctly. So, add a new intermediate variable, desc, to store the result of the dma_pool_alloc() call. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- This patch is part of a work done in parallel of what is currently worked on by Kees Cook. My patches are only related to corner cases that do NOT match the semantic of his Coccinelle script[1]. [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci --- drivers/dma/pxa_dma.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)